fix-03: track redeemed kyc coupons

[fforbeck]

Proposed Changes

• Members that already joined the DAO using a KYCed coupon, shouldn't be able to join again using the same coupon.

[codecov]

Codecov Report

Merging #509 (cb3a24d) into master (bef1c72) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head cb3a24d differs from pull request most recent head 69dce7b. Consider uploading reports for the commit 69dce7b to get more accurate results

@@            Coverage Diff             @@
##           master     #509      +/-   ##
==========================================
+ Coverage   82.27%   82.30%   +0.02%     
==========================================
  Files          53       53              
  Lines        1851     1854       +3     
  Branches      430      431       +1     
==========================================
+ Hits         1523     1526       +3     
  Misses        328      328              

Impacted Files	Coverage Δ
contracts/adapters/voting/OffchainVoting.sol	41.25% <ø> (ø)
contracts/adapters/KycOnboarding.sol	93.33% <100.00%> (+0.27%)	⬆️

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